Miniature chiral beamsplitter based on gyroid photonic crystals

Journal name:
Nature Photonics
Year published:
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The linearly polarizing beamsplitter1, 2 is a widely used optical component in photonics. It is typically built from a linearly birefringent crystal such as calcite, which has different critical reflection angles for s- and p-polarized light3, leading to the transmission of one linear polarization and angled reflection of the other. However, the analogue for splitting circularly polarized light has yet to be demonstrated due to a lack of natural materials with sufficient circular birefringence. Here, we present a nano-engineered photonic-crystal chiral beamsplitter that fulfils this task. It consists of a prism featuring a nanoscale chiral gyroid network4, 5, 6, 7, 8, 9, 10 and can separate left- and right-handed circularly polarized light in the wavelength region around 1.615 µm. The structure is fabricated using a galvo-dithered direct laser writing method and could become a useful component for developing integrated photonic circuits that provide a new form of polarization control.

At a glance


  1. The CBS is built from a cubic chiral srs-network and with the ability to split circularly polarized light.
    Figure 1: The CBS is built from a cubic chiral srs-network and with the ability to split circularly polarized light.

    a, Illustration of the chiral beamsplitting phenomenon, where LCP light (blue) is transmitted and RCP light (red) is reflected. b, Experimental set-up for characterization of the CBS. The intensity of transmitted and reflected light is measured by imaging the diffusely scattered light from the scattering bar. c, Close-up view of the CBS under illumination. d, Illustration of the experimental imaging system. The regions of interest where reflected and transmitted signals from the CBS are measured by the camera are labelled R and T, respectively.

  2. Optical characterization of the polymer srs-network along [001] with a = 1.2 [micro]m.
    Figure 2: Optical characterization of the polymer srs-network along [001] with a = 1.2 µm.

    Red and blue curves represent RCP and LCP incident light, respectively. a, Experimentally measured transmission spectra. Inset: SEM image of an srs-network. Scale bar, 2 µm. b, Numerically simulated transmission spectra. c, Theoretical bandstructure for the polymer srs-network. The size of the points is related to the coupling coefficient β, and the colour is given by the circular dichroism index C, where RCP is red, LCP is blue and unpolarized is black1. The dashed vertical lines highlight the fundamental band edge at 1.55 µm, the circular dichroism band at 1.5 µm, and the low-coupling band at 1.45 µm.

  3. SEM images of the CBS fabricated using GD-DLW and consisting of 64,000 unit cells of the srs-network (768,000 individual rods).
    Figure 3: SEM images of the CBS fabricated using GD-DLW and consisting of 64,000 unit cells of the srs-network (768,000 individual rods).

    a, Angled view showing the CBS at the edge of the glass substrate and surrounded by the dielectric scattering bars BT and BR. b, Top view along the z-direction. c, Zoomed-in view of the highlighted area in a. d, Zoomed-in view of the highlighted area in b. Scale bars, 20 µm (a,b) and 2 µm (c,d).

  4. Characterization of the CBS under excitation along [100] (that is, at 45[deg] to the input surface) for LCP (blue) and RCP (red) incident light.
    Figure 4: Characterization of the CBS under excitation along [100] (that is, at 45° to the input surface) for LCP (blue) and RCP (red) incident light.

    a, At a wavelength of 1,570 nm, both LCP and RCP light are completely reflected. b, At a wavelength of 1,615 nm, LCP light is preferentially transmitted and RCP light is preferentially reflected. c, At a wavelength of 1,650 nm, both LCP and RCP light are completely transmitted. d, Spectral plot of transmission (solid lines) and reflection (dashed lines) of RCP (red) and LCP (blue) light.


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  1. Centre for Micro-Photonics and CUDOS, Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, Hawthorn, Victoria 3122, Australia

    • Mark D. Turner,
    • Qiming Zhang,
    • Benjamin P. Cumming,
    • Gerd E. Schröder-Turk &
    • Min Gu
  2. CRC for Polymers, 8 Redwood Drive, Notting Hill, Victoria 3168, Australia

    • Mark D. Turner
  3. Theoretische Physik, Friedrich-Alexander Universität Erlangen-Nürnberg, Staudtstrasse 7B, Erlangen, Germany

    • Matthias Saba &
    • Gerd E. Schröder-Turk


M.D.T. performed the numerical simulations, structural design, direct laser writing and experimental characterization. M.S. performed theoretical calculations. Q.Z. performed experimental characterization. B.C. suggested the galvo-dithering method and performed the substrate cleaving. G.E.S.T. and M.G. participated in the design of experiments and data analysis. All authors contributed to writing the manuscript.

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